1. Field of Invention
The present invention relates to a card reading device, in particular, to a card reading device capable of reducing loading effects.
2. Related Art
Accompanying with developments of technology, medical insurance cards, credit cards, banking cards, identification cards and passports that are frequently used in our daily life, have been developed as digital identification cards such as magnetic stripe cards or IC cards. The user's individual information is recorded in the digital identification card; for example, a non-contact ticket-paying system used in a ticket identification system. In the recent years, Radio Frequency Identification (RFID) technology has become more mature, many credit card and banking cards have been introduced to the market as a non-contact card type. The user only has to put the non-contact card on a non-contact reading device for sensing to complete a payment transaction. Therefore the transaction time is dramatically reduced; the user does not need to worry about leaving the card in the contact card reader and losing it. However, since the non-contact reading device uses electromagnetic sensing technology, it is very easy for the non-contact reading device to be interfered by the external materials surrounding the card reader. In particular, a metal housing may cause the deformation of antenna loading; an over shifted modulation of signal loading will result in operation failure when sensing a non-contact card. For instance, a non-contact reading device disposed in a parking lot might be malfunctioned due to the electromagnetic-wave reflections of its metal housing.
Since magnetic field generated from the antenna of the reading device varies according to the shapes and materials of a nearby metal, also the magnetic field will generate different Eddy current and different loading effects by a reversed electromotive force according to the Lenz's Law, the card reading will not be able to normally read the signals sent from the non-contact card. Moreover, the electromagnetic-wave absorption materials used for the reader's antenna are usually selected to match a certain metal portion on which a certain antenna design is installed, without considering various installation environments (such as the metal characteristic and shape at the installation portion). If an antenna is installed in a new housing with a different metal characteristic and shape, the antenna matching has to be adjusted. Otherwise, it is easy to cause a card-reading failure.